This invention relates, in general, to the bonding of two surfaces, and more particularly, to an apparatus and method for bonding two semiconductor wafers.
The bonding of two semiconductor wafers together offers many advantages in the manufacturing of semiconductor devices. Devices that are manufactured in this manner offer higher performance for high density CMOS, high voltage, and high frequency devices. Many theories have been discussed in the literature about actual bonding mechanisms for joining two wafers together. One such theory is Van der Waals bonding or dipole bonding. Van der Waals bonding is caused by an electrical interaction of dipoles in two bodies. This theory as well as others are discussed in greater detail by J. Haisma, G. A. C. M. Spierings, U. K. P. Biermann and J. A. Pals, "Silicon-on-Insulator Wafer Bonding-Wafer Thinning Technological Evaluations," Japanese Journal of Applied Physics, Vol. 28, No. 8, August, 1989, pages 1426-1443. Generally, the conventional process of wafer bonding is achieved by quickly cleaning the surfaces to be bonded, manually placing the surfaces in contact with each other, and further pressing the surfaces together by a hand rolling pin device. This process results in poor bonding and many voids due to contamination.
Contamination of the bonding surface is a major concern in being able to achieve void free bonding of the two surfaces. Organic film and particle contamination are two main contamination types that prevent manufacturing high quality void free bonded surfaces. Organic contamination of semiconductor surfaces has been shown to occur by simple storage of surfaces as described by V. Lehmann, U. Gosele, and K. Mitani, "Contamination Protection of Semiconductor Surfaces by Wafer Bonding," Solid State Technology, April 1990, pages 91-92. Particles, another form of contamination that is well known in the industry also has been shown to participate in the void formation of bonded surfaces. Therefore, a method that enables the removal of contamination and prevents the occurrence of recontamination of the bonding surfaces is highly desirable.